1. Field of the Invention
The present invention relates to a foot massage machine, and more particularly, to a drive unit thereof.
2. Description of the Prior Art
The so-called foot massage machine 1, as shown in FIG. 1, includes a laterally shiftable massage seat 12 at top of a housing 11. The massage seat 12, as shown in FIGS. 2 and 3, is driven by a slider assembly 13 inside of the housing 11. The slider assembly 13 brought into rotation by means that an eccentric block 15 is driven by a motor 14. In addition, a pulley 151 is mounted at outer side of the eccentric block 15 for engaging into a longitudinal groove 131. As a result, the pulley 151 is movable upward and downward in the longitudinal groove 131 when it rotates. Meanwhile, the slider assembly 13 is driven to move rightward and leftward on two shaft rods 161 at top and bottom of a frame body 16. Thus, the function to massage the feet is achieved. This kind of this design is disclosed in U.S. Pat. No. 5,107,822, TW Patent No.: 145682, 285036, 251457, etc. Though the conventional drive unit of the foot massage machine is simple in configuration, it has the following drawbacks:
1. It's not an optimal state for the mechanical design in making use of the pulley 151 sliding in the longitudinal groove 131 of the slider assembly 13. The reason lies in that the sliding element directly rubs rather than moving the driven body. Moreover, most of the slider assembly 13 is made by plastic injection molding for adapting to the production's needs. In order that the pulley 151 can be movable upward and downward in the longitudinal groove 131 made from plastic and the slider assembly 13 is driven by the revolving force, the contact of the pulley 151 with the longitudinal groove 131 can't be too close. Otherwise, the friction will be too large for moving the slider assembly 13. However, a clearance between two moving elements will produce noise. Especially, the inner wall of the longitudinal groove 131 will be rubbed when the pulley 151 repetitively moves thereon. As a result, the noise becomes bigger and the service life is therefore reduced. PA0 2. The longitudinal groove 131 slides on the shaft rods 161 by means of two shaft grooves 132 thereof so that the above-mentioned drawback will also be created. The closer the contact between two shaft grooves 132 and the shaft rods 161 is, the larger the drive force of the motor 14 will be and the more the electricity is consumed, or even the motor 14 is burnt down due to the overload. If a clearance between the shaft grooves 132 and the shaft rods 161 is present, the slider assembly 13 will easily shake during the rightward or leftward shift while the noise is great.
Accordingly, the foot massage machine configured with the above-mentioned structure has drawbacks of short service life and great noise except its cheap price.
In order to remove the above-mentioned drawbacks, another drive slider assembly (see FIG. 4) is developed. A motor 14 brings an eccentric block 15 in motion which moves a connecting rod 17 connected with the slider assembly 13 so that the slider assembly 13 can be shifted rightward and leftward on the shaft rods 161. This kind of design is disclosed in TW 226097, 217532, etc. This design can remove the above-mentioned drawbacks of directly rubbing the longitudinal groove 131 by the pulley 151; however, the connecting rod 17 can't be too short in order that the slider assembly 13 effectively performs a rightward and leftward displacement. Thus, the motor 14 has to be installed at one side of the frame body 16 rather than at the center of the above-mentioned structure. Accordingly, the center of gravity lies more at one side of the motor 14 in addition to occupying more space. Besides, the rightward and leftward shift of the slider assembly 13 on the shaft rods 161 also has the rubbing problem of the above-mentioned embodiment so that the great noise and the short service life are its drawbacks.